Phonebook/Services/ContactService.cs

using ClosedXML.Excel;
using Phonebook.Utils;
using Contact = Phonebook.Models.Contact;

namespace Phonebook.Services;

public class ContactService
{
    private readonly DatabaseService _databaseService;

    public Action? OnContactsUpdated;

    public ContactService(DatabaseService databaseService)
    {
        _databaseService = databaseService;
    }

    public void InvokeUpdateContacts()
    {
        OnContactsUpdated?.Invoke();
    }

    public async Task ClearAllContacts()
    {
        await _databaseService.ClearAll();
    }

    public async Task<List<Contact>> GetAllContacts()
    {
        return await IPlatformApplication.Current!.Services.GetService<DatabaseService>()!.GetContactsAsync();
    }
    
    private static async IAsyncEnumerable<Contact> GetPhoneContacts()
    {
        var contacts = await Contacts.Default.GetAllAsync();
        
        foreach (var userContact in contacts)
        {
            var contact = new Contact();

            contact.Name = userContact.DisplayName;

            var firstPhoneNumber = userContact.Phones.FirstOrDefault();

            contact.PhoneNumber = firstPhoneNumber != null ? 
                firstPhoneNumber.PhoneNumber : "";
            
            var firstEmail = userContact.Emails.FirstOrDefault();

            contact.Email = firstEmail != null ? 
                firstEmail.EmailAddress : "";

            contact.Address = "";
            contact.Description = "";
            contact.PhotoPath = "";

            yield return contact;
        }
    }

    public async Task ImportFromLocalContact()
    {
        var createList = new List<Contact>();
        
        await foreach (var phoneContact in GetPhoneContacts())
        {
           var foundId = await _databaseService.SearchIdByNameOrDefault(phoneContact);
           
           if(foundId.Id != 0) 
               continue;

           createList.Add(phoneContact);
        }
        
        await _databaseService.SaveContactsAsync(createList);
        InvokeUpdateContacts();
    }
    
    public async Task ExportToXlsx()
    {
        try
        {
            var allContacts = await GetAllContacts();

            if (allContacts.Count <= 0)
            {
                return;
            }

            var fileName = $"contacts_{DateTime.Now:yyyyMMdd_HHmmss}.xlsx";
            var localPath = Path.Combine(FileSystem.CacheDirectory, fileName);

            using (var workbook = new XLWorkbook())
            {
                var worksheet = workbook.Worksheets.Add("Contacts");

                worksheet.Cell(1, 1).Value = "Id";
                worksheet.Cell(1, 2).Value = "Name";
                worksheet.Cell(1, 3).Value = "PhoneNumber";
                worksheet.Cell(1, 4).Value = "Email";
                worksheet.Cell(1, 5).Value = "Address";
                worksheet.Cell(1, 6).Value = "Description";
                worksheet.Cell(1, 7).Value = "PhotoPath";
                
                for (var i = 0; i < allContacts.Count; i++)
                {
                    var contact = allContacts[i];

                    worksheet.Cell(2 + i, 1).Value = contact.Id;
                    worksheet.Cell(2 + i, 2).Value = contact.Name;
                    worksheet.Cell(2 + i, 3).Value = contact.PhoneNumber;
                    worksheet.Cell(2 + i, 4).Value = contact.Email;
                    worksheet.Cell(2 + i, 5).Value = contact.Address;
                    worksheet.Cell(2 + i, 6).Value = contact.Description;
                    worksheet.Cell(2 + i, 7).Value = contact.PhotoPath;
                }
                
                workbook.SaveAs(localPath);
            }

            await Share.Default.RequestAsync(new ShareFileRequest
            {
                Title = "Сохранить контакты",
                File = new ShareFile(localPath)
            });

        }
        catch (Exception ex)
        {
          
        }
    }
}